1. Field of the Invention
The present invention relates to welding equipment and particularly to a mobile arrangement for laying a continuous pipeline. Most advantageously the invention can be used in laying main oil and gas pipelines, water supply systems, in-pipe pneumatic conveyors etc.
2. Description of the Prior Art
Since 1950, when resistance welding was used for the first time in laying pipelines, the improvement of equipment for this type of welding had as its aim a higher efficiency in assembling and welding of pipes into a continuous pipeline. The method of laying a continuous pipeline comprises a number of various operations which, in most cases, can be carried out in succession only. Therefore, saving of time spent for preparatory and auxiliary works carried out between operations can appreciably decrease the time duration of laying a pipeline and will make it possible to take advantage of such highly productive method as resistance welding. It is to be noted that making of butt-type joint only takes 0.5 to 1 sec., flash removal takes 1 to 5 sec, and thermal treatment of one weld takes 5 60 sec. At the same time the preparatory and auxiliary works carried out between operations with the aid of conventional equipment take 10 to 30 min. The urgency of the problem under consideration is apparent when it is considered that the quantity of welds to be made in a main pipeline may be more than 100,000. The results of the investigation of the possibilities of the conventional equipment prove that this problem has not been adequately solved up till now.
Known in the art is a mobile arrangement for resistance welding of 529 mm in diameter pipes into a continuous pipeline (see, for instance, V. K. Lebedev, G. V. Gorbunov, Kontaktnaya svarka truboprovodov, "Reklama" Publishers, Kiev, 1968, p.18). This arrangement comprises a pipe-laying means having a jib with a welding head suspended therefrom. The welding head encompasses the pipes being welded and is supported by their walls through rollers. The pipelaying means mounts a power-supply set connected with the welding head by an electric cable. It follows from the description of the arrangement that the latter ensures only the welding of pipes, whereas such operations as inner flash removal and outer flash removal are to be carried out by hand.
There is also known in the art a more efficient mobile arrangement for laying pipelines (see V. K. Lebedev, G. V. Gorbunov, Kontaktnaya svarka truboprovodov, "Reklama" Publishers, Kiev, 1968, p 23). The arrangement comprises an in-pipe resistance welding apparatus supported by the walls of the pipeline and connected with a source of electric power. The apparatus incorporates a self-contained drive and an internal flash trimmer. The arrangement is provided with an outer flash trimmer which is suspended from the jib of the pipe-laying means. In front of the latter there is disposed another pipe-laying means whose jib carries a suspension with supporting rollers for supporting the pipeline. The above suspension is attached directly to the rope passed over the end of said jib.
An obvious advantage of the described welding arrangement consists in that it permits not only the welding process but also flash removal to be mechanized. However the productivity of this welding arrangement is appreciably restricted by the necessity of carrying out a number of auxiliary operations. For instance, in order to remove flash after welding the pipes, it is necessary to lower the pipeline onto supports or to heap up soil thereunder by bulldozer, to back away the pipelaying means carrying the suspension, to make place for the pipe-laying means carrying the outer flash trimmer, to bring the latter pipelaying means to the weld and only then to remove the outer flash. It is to be noted that the flash is best to remove in hot state immediately after welding, but this is prevented by the necessity of carrying out the above auxiliary operations.